R 350 CDI, black smoke, jerky at low revs, soot on exhaust, occasional limp mode

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npritch

New Member
Joined
Sep 22, 2021
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20
Location
Gloucestershire
Car
R 350 CDI, 2011, 3.0 litre V6 diesel
Hi - I'd be grateful if someone could help me diagnose a problem I am having...
The car has done about 180,000 miles but has run beautifully until recently. When driving slowly with revs between 1000 - 2000 the car is extremely "jerky" - as though there is either not enough - or too much fuel being pumped in. The problem disappears when the revs are higher than 2000 and if I am travelling at speed - however occasionally the car goes into "limp" mode - which is reset if the car is switched off and restarted. The car idles normally - though perhaps at a little higher revs (800 instead of 500...?). There is no engine warning light. I noticed yesterday that there is a lot of soot around the exhaust pipes - and when stationary and the accelerator is pushed there is a brief puff of black smoke. I have not noticed this smoke before - and I don't think it is blowing out under normal driving conditions. The car has just been serviced - so I assume the air filter was changed. I've read that it could be a dirty EGR valve - but also could be to do with the injectors. Any advice or ideas of what the problem could be would be greatly appreciated.
Sadly, though I love the car - given it's age and mileage I can't afford to throw big money at it - but I can't help feeling that the problem is relatively minor...
Thanks in advance.
 
Hello and welcome . I think most on here would suggest you get the codes read before going any further. Are you able to pop back to the garage that just serviced it and ask them to run a scan on it ?

Best of luck.
 
If there are no codes then a good start would be to look at the turbo actuator. They get a bit sticky inside (carbon dust/dried grease) over time. A refurb is the way to go, mine was £96 from TurboVanes with 2 yrs warranty.

However as always with these things getting the live data read is useful.
 
Thank you Pete for getting back to me. About 2 months ago the engine warning light came on - this was DPF issue which was solved - the light hasn't come on since. I asked the garage to check the issue of "limp mode" and erratic running at low revs - they reckoned that they had sorted out the problem with the work on the DPF - they were wrong - so no great confidence in them. Attached is a pdf of the codes I got from my reader just now - any help? Many thanks
 

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If there are no codes then a good start would be to look at the turbo actuator. They get a bit sticky inside (carbon dust/dried grease) over time. A refurb is the way to go, mine was £96 from TurboVanes with 2 yrs warranty.

However as always with these things getting the live data read is useful.
Thanks Larkone - I just uploaded a pdf of the readout I got just now - not sure if it reveals anything conclusive?
 
The last code P0299 indicates a boost leak - time for a smoke test.
 
The last code P0299 indicates a boost leak - time for a smoke test.
Thank you Larkone - that would make sense. Is that likely to be revealing whilst stationary - as the problem only appears when the car is on the move?
 
That's the point, a smoke test pumps smoke through the pipework when stationary so you can trace leaks
 
That's the point, a smoke test pumps smoke through the pipework when stationary so you can trace leaks
Thanks Larkone. Yes I know about the smoke test - my query was as the main problem only shows when travelling it may not show up when stationary? But I’ll book it in and hope for the best. Thanks again for your help.
 
Hi Larkone - another forum suggested a problem with the turbo actuator (I had a quick look - it seems to be working - ie the arm moves). And/or with the PCV valve - but wouldn't that produce blueish smoke rather than the black sooty smoke I'm getting?
 
Yes re smoke but at 180K miles the PCV is likely to have gone - rubber diaphragm goes hard and splits which lets oil through - about £100. Mine had gone at 133K. This failing is a given but is not likely to cause the performance issues. Link here - OM642 PCV Upgrade | Engine

The turbo actuator is another problem because the electric motor inside sheds carbon dust which mixes with the grease and gums up the drive cogs. They can also burn out some connection links inside. You can 'service' them, clean and re-grease and I did mine when I did the PCV. They look like they are functioning but the reality is they are not functioning properly, hence they can cause 'jerkyness'.

However I recently replaced (155K) this with a exchange refurb from TurboVanes (£96, 2 year warranty) and the difference was well worthwhile, especially as it significantly improved consumption and bought back that smooth endless punch in the back these engines have. This could be causing your performance/jerky issues however I would still check for leaks first with a smoke test as this will tell you if you have any splits in pipes or leaking seals. Again at that mileage highly likely and it is the least cost to check and fix.

Sorry but it is really difficult to pinpoint exactly what your problem is but at that mileage you can expect seals, diaphragms, rubber and plastic pipes to start failing and actuators getting arthritic so start with the easier and cheapest first - leaks. Otherwise pay to get it on STAR and get the live data read.
 
One other thing... the engine warning light came on today and the code from the reader was as follows not sure if it sheds more light?

P0299
Raw code: 0299
ECU: Engine control unit
Status: Confirmed
OBDII: Turbocharger (TC)/supercharger (SC) - low boost


============2==============
1335552
Raw code: 146100
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear

============3==============
1356288
Raw code: 14B200
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear, Test not completed during this operation cycle

============4==============
1366784
Raw code: 14DB00
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear, Test not completed during this operation cycle

============5==============
1194240
Raw code: 123900
ECU: Engine control unit
Status: Pending, Confirmed, Test failed since last DTC clear, Test not completed during this operation cycle, Warning indicator requested


============6==============
1363712
Raw code: 14CF00
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear, Test not completed during this operation cycle

============7==============
1357568
Raw code: 14B700
ECU: Engine control unit[Archive (inactive)]
Status: Test failed since last DTC clear, Test not completed during this operation cycle
 
I had similar symptoms and it was the EGR valve. I cleaned it as best I could but was only fixed with a replacement. Codes were not obvious this was the way to go to diagnose either. As above, it could be many other issues also.
 
Thanks Phil - I'll add that one to the long list...
 
The ECU uses two control loops for the turbo, a position controller and a boost controller. P0299 says the measured boost does not equal the demanded.
P1239 says the actuator feedback position does not the demanded position. Specifically it's asking for vanes to close and they are not. You can expect P0299 if you have P1239.
In your tests, if you removed the plug, it's to be expected. If not, as others have said, it may appear to move, but might not be properly.
 
Thanks Supernoodle. That’s really helpful. Looks like it could be a problem with the actuator then?
 
Thanks Supernoodle. That’s really helpful. Looks like it could be a problem with the actuator then?
Now that there is a confirmed fault for the actuator I would expect that it has given up trying to do close loop control of the turbo. If so and the actuator was the cause of your reported jerkiness this it should feel different when driving.
If you had a decent tester the freeze frame data would show under what conditions the fault set. If it was the same conditions you report the jerkiness that would be reassuring.
My only reservation is even if the actuator was moving around, all its doing is moving the VGT vanes, which in turn changes turbine speed and hence boost. In the scheme of things that's slow. That would normally create what I'd call hesitation and maybe surging. Jerkiness I would use to describe some rapid changes in engine speed.
So this may be a factor in the black smoke, but not convinced on the jerkiness.
To add to the woes, if you have a DPF you shouldn't see black smoke or soot on the tailpipe. If you do that's probably a cracked DPF.
 
Thanks again Supernoodle really helpful - definitely "hesitation and surging" is a much better description of what I am experiencing - as mentioned only between 1000 - 2000 revs... so the actuator looks to be the most likely culprit - not sure if I am brave enough to try to swap the actuator out so I guess a reluctant trip to my garage for a more detailed look is the way to go... though they will probably tell me it's a new turbo...
I did have a DPF fault before - the garage removed it and cleaned it and it seemed to be fine. Clearly there is something else going on which caused that DPF fault initially - so I hope that by not dealing with the root cause they haven't screwed up the DPF again as they are expensive...
 
I have the same thing. It’s on very light throttle only? I’d call it a gentle juddering

It’s very intermittent and no error codes for me though.

I’m tempted to clean the turbo actuator myself.
 

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